ASHRAE Journal - February 2020 - 41

ASHRAE - CELEBRATING 125 YEARS

inadvertently created a
whole new component category. Soon, others improved
upon Thompson's original
design. Danfoss' founder,
Mads Clausen, ﬁrst entered
the refrigeration business
by selling a TXV of his own
design, the ARV, followed
soon after by the TRV.

Design Modiﬁcations Over
The Years

FIGURE 1 TXV.

FIGURE 2 Cycle.

Compressor
4. Gas: Low Pressure
And Low Temperature

1. Gas: High Pressure
And High Temperature

Evaporator

Condenser

3. Gas/Liquid Mix:
2. Liquid: High Pressure
Low Pressure and Low
And Median Temperature
Temperature
Throttle Device

FIGURE 4 Pressures.

FIGURE 3 TXV parts.

While early TXVs
Bulb Pressure
Diaphragm
(such as the one seen in
Power Element
Figure 6 (Page 42) were simBulb Pressure
pler than today's models,
the basic formula created
by Thompson more than 90
Equalization Area:
Evaporation Pressure
years ago has not changed.
Whether old or new, all
Spring
Evaporator
TXVs have a diaphragm,
Pressure
Pressure
Superheat Setting Spring:
a power element, a setSpring Pressure
ting spring and an oriﬁce,
though the size, shape and material
equalizer line connected to the evapFIGURE 5 Harry Thompson patent.
of each piece may change. As manuorator outlet. Internally equalized
facturing technology has improved
valves sense the evaporator pressure
and new materials developed, manu- at the outlet of the valve. Of the airfacturers have been able to adapt
conditioning systems in the US that
TXVs to a wider variety of applicause TXVs, the majority-if not all-use
tions. In fact, the differences between valves that are externally equalized.
various types of modern TXV models
Conventional Port Versus Balanced Port Design
are greater than the differences
Figure 8 (Page 42) shows two difbetween early and modern models.
ferent TXV port designs. In convenDifferences in Various TXV Types
tional or single port designs, the
Internal Versus External Equalization
diaphragm can be inﬂuenced by
Figure 7 (Page 42) shows two types of pressure changes in the condenser.
TXVs, those available with internal
The general rule of thumb is that a
or external pressure equalization.
conventional port design works best
Externally equalized valves are recin systems with less than ﬁve tons
ommended for multi-circuit systems of cooling capacity, while larger sysbecause they account for excessive
tems work best with a balanced port
pressure drops coming from disdesign (though it is not uncommon to
tributors and through the evaporaaffecting the opening of the valve,
use a balanced port valve in smaller
tor-externally equalized valves sense systems). A balanced port design
necessitating the use of a packing
the evaporator pressure from the
isolates the condenser pressure from gland. However, the use of a packing
FEBRUARY 2020

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ASHRAE JOURNAL

41

https://www.ashrae.org/

ASHRAE Journal - February 2020

Table of Contents for the Digital Edition of ASHRAE Journal - February 2020

Contents
ASHRAE Journal - February 2020 - Intro
ASHRAE Journal - February 2020 - Cover1
ASHRAE Journal - February 2020 - Cover2
ASHRAE Journal - February 2020 - Cover2a
ASHRAE Journal - February 2020 - Contents
ASHRAE Journal - February 2020 - 3
ASHRAE Journal - February 2020 - 4
ASHRAE Journal - February 2020 - 5
ASHRAE Journal - February 2020 - 6
ASHRAE Journal - February 2020 - 7
ASHRAE Journal - February 2020 - 8
ASHRAE Journal - February 2020 - 9
ASHRAE Journal - February 2020 - 10
ASHRAE Journal - February 2020 - 11
ASHRAE Journal - February 2020 - 12
ASHRAE Journal - February 2020 - 13
ASHRAE Journal - February 2020 - 14
ASHRAE Journal - February 2020 - 15
ASHRAE Journal - February 2020 - 16
ASHRAE Journal - February 2020 - 17
ASHRAE Journal - February 2020 - 18
ASHRAE Journal - February 2020 - 19
ASHRAE Journal - February 2020 - 20
ASHRAE Journal - February 2020 - 21
ASHRAE Journal - February 2020 - 22
ASHRAE Journal - February 2020 - 23
ASHRAE Journal - February 2020 - 24
ASHRAE Journal - February 2020 - 25
ASHRAE Journal - February 2020 - 26
ASHRAE Journal - February 2020 - 27
ASHRAE Journal - February 2020 - 28
ASHRAE Journal - February 2020 - 29
ASHRAE Journal - February 2020 - 30
ASHRAE Journal - February 2020 - 31
ASHRAE Journal - February 2020 - 32
ASHRAE Journal - February 2020 - 33
ASHRAE Journal - February 2020 - 34
ASHRAE Journal - February 2020 - 35
ASHRAE Journal - February 2020 - 36
ASHRAE Journal - February 2020 - 37
ASHRAE Journal - February 2020 - 38
ASHRAE Journal - February 2020 - 39
ASHRAE Journal - February 2020 - 40
ASHRAE Journal - February 2020 - 41
ASHRAE Journal - February 2020 - 42
ASHRAE Journal - February 2020 - 43
ASHRAE Journal - February 2020 - 44
ASHRAE Journal - February 2020 - 45
ASHRAE Journal - February 2020 - 46
ASHRAE Journal - February 2020 - 47
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ASHRAE Journal - February 2020 - 49
ASHRAE Journal - February 2020 - 50
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ASHRAE Journal - February 2020 - 52
ASHRAE Journal - February 2020 - 53
ASHRAE Journal - February 2020 - 54
ASHRAE Journal - February 2020 - 55
ASHRAE Journal - February 2020 - 56
ASHRAE Journal - February 2020 - 57
ASHRAE Journal - February 2020 - 58
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ASHRAE Journal - February 2020 - 60
ASHRAE Journal - February 2020 - 61
ASHRAE Journal - February 2020 - 62
ASHRAE Journal - February 2020 - 63
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ASHRAE Journal - February 2020 - 79
ASHRAE Journal - February 2020 - 80
ASHRAE Journal - February 2020 - Cover3
ASHRAE Journal - February 2020 - Cover4
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